Apparatus and method for setting a valve lift

ABSTRACT

An apparatus and a method are proposed for adjusting a valve lift, particularly a valve needle lift of an injection valve of an internal combustion engine, wherein a valve seat, which is preset in a housing of the valve (20), is axially displaceable in the housing by means of plastic deformation. The apparatus is provided with an adjustment device (50) which generates a feeding motion for a pressing tool (53, 55) in the direction of the plastic deformation and with a measuring device (30) which determines the valve lift that is changeable by way of the plastic deformation of the valve seat and compares the valve lift with a preset desired value, with the adjustment device (50) being controllable by way of the desired value/actual value comparison. The pressing tool (53, 55) is fed by means of a first and, if necessary, by means of at least one further feeding process. From the values obtained by the first feeding process a characteristic is formed during a learning phase, from which a further feed for the respective further feeding process is determined.

PRIOR ART

The invention relates to an apparatus and a method for setting a valvelift, in particular a valve needle lift of an injection valve of aninternal combustion engine of the generic type of the respectiveindependent claims.

An injection valve according to DE-A1 40 26 721 has a valve seat body ina valve housing, with the valve seat body being connected to anapertured body which is fixed with respect to the housing. A valveneedle with a valve closing body is seated on the valve seat body. Theprecise setting of the valve needle lift takes place on the completelyassembled injection valve by plastically deforming the apertured body,which is fixed with respect to the housing, in the direction of thevalve closing body. The deformation of the apertured body reduces thevalve needle lift from a preset magnitude to a required valve lift. Thevalve needle lift defines the static flow volume of the injection valve.

An efficient valve production requires that the integration of thesetting of the valve lift into an assembly line production process bepossible. This also means that it must be possible to set the valve liftwith a high degree of repeating accuracy.

ADVANTAGE OF HE INVENTION

The apparatus having the characterizing features of claim 1 has theadvantage that a shifting of the valve seat is possible with a highdegree of repeating accuracy by means of plastic deformation of theapertured body at a high feeding speed of the pressing punch. In thismanner a cycle time is reached for the setting of the valve lift whichallows an integration into an assembly line production process. Themethod according to the invention is based on a self-learning settingsequence for the setting of the lift and is comprised of a learningphase and a final lift-setting phase. Due to the optimization of theparameters achievable in this manner, highest quality is accomplished ata cycle time which is as short as possible. Furthermore, it is alsopossible to use this method for different types of valves by editing theparameters.

The measures listed in the dependent claims allow advantageousmodifications and improvements of the apparatus according to theinvention. It is especially advantageous to implement the forceadmission via a spring element. In this process, the spring element actsas transmission and allows for a fast feeding speed of the adjustmentdevice. The arrangement of a force sensor in the force transmissionchain allows a good approach point recognition so that, in addition, arelatively high approach speed is possible. A high-resolution pathmeasuring system is seated on the valve and can be displaced verticallyso that the effects of elasticities of the apparatus can be eliminated.A special clamping arrangement ensures that the valve orients itselffreely according to an infeed plane surface and thus is given a definedposition.

DRAWING

In the following, the invention is described in greater detail by way ofan embodiment which is shown in the drawing. FIG. 1 shows a crosssection of a nozzle-side end of an internal combustion injection valve,

FIG. 2 a fundamental representation of a side view of the apparatusaccording to the invention,

FIG. 3 a sectional representation according to the lines III--IIIpursuant to FIG. 2,

FIG. 4a a first section of a process sequence schedule to determine avalve lift during setting and FIG. 4b a second section of the processsequence schedule according to FIG. 4a.

EMBODIMENT

The injection valve 20, whose nozzle-end section is partially shown inFIG. 1, has a tubular seat support 21 with a longitudinal opening 23 inwhich, for example, a tubular valve needle 24 is arranged which restswith a spherical valve closing body 25 in a guide opening 26 of a valveseat body 27. The valve seat body 27 is concentrically and fixedlywelded to an apertured body 28 at the end face facing away from thevalve closing body 25. The apertured body 22 has a pot-shaped crosssection having a circumferential retaining edge 29. In the longitudinalopening 23, the apertured body 28 is connected with the retaining edgeto the wall of the longitudinal opening 23, for example, by way of acircumferential and tight weld seam 22. The position of the valve seatbody 27 in the longitudinal opening 23 fixed by the welding of theapertured body 28 determines a presetting of the valve lift of the valveneedle 24. More detailed explanations regarding the structure and effectof the injection valve can be taken from DE-A1 40 26 721.

The fundamental representation of the apparatus according to theinvention pursuant to FIG. 2 shows a solid frame 11 mounted on a baseplate 10, a measuring device 30, a clamping device 40 fastened to theframe 11, and an adjustment device 50. A column guide 14 is mounted tothe frame 11 or to the base plate 10 by means of a guide bar 15. Theguide bar 15 is connected to an extension arm 16 to which the measuringdevice 30 is affixed. Furthermore, a piston bar 17 of a pneumaticcontrol cylinder 18 acts on the extension arm 16. An injection valve 20is clamped in the center and from the bottom to the top in the clampingdevice 40.

The measuring device 30 is a high-resolution measuring system and isprovided with a probe measuring device 31 which acts on a path sensingelement 32. The probe measuring device 31 is provided with a measuringcarriage 33 with a measuring gage 34, guided in a high-precision ballguide which is not shown, with the measuring gage 34 being comprised ofhard metal. The path sensing element 32 is fixedly connected to themeasuring carriage 33. A replaceable stop 35 is attached to the housingof the probe measuring device 31; the stop paths for different injectionvalves can be defined by means of the stop.

The measuring device 30 is fed by the feeding cylinder 18 such that themeasuring gage 34 extends through the hollow valve needle 24 and isseated on the valve closing body 25. Afterwards, the stop 35 rests onthe housing 21 of the injection valve. The path sensing element 32supplies an electrical measuring signal which serves to detect the valvelift and is evaluated by the control for the setting process. A lightbarrier is provided to monitor the running-on of the measuring gage 34;if activated, the light barrier causes the feeding cylinder 18 to returnthe measuring device 30 into the initial upper position.

The configuration of the clamping device 40 and of the adjustment device50 is shown in FIG. 3. The clamping device 40 is comprised of a solidsupport 43 having a top section 41 and a bottom section 42. Ahorizontally displaceable centering slide 44 comprised, for example, oftwo parts is arranged between the support sections 41 and 42, with thecentering slide, while having an axial play, clamping the injectionvalve 20 at an undercut. For the guiding of the slide 44 without anyplay, a ball detent which is not shown is provided in the bottom supportsection 42. A receiver 45 having center bores for the injection valve 20which are not shown is embedded in the top support section 41. Thecentering slide 44 is displaced axially, for example, by actuatingelements 46 which are not shown in detail, with the movement beingcarried out by pneumatic cylinders which are not shown in detail. Thebottom support section 42 has a recess 47 through which extends thenozzleside end of the injection valve 20.

The adjustment device 50 with a pressing unit 51 and a feeding unit 52is arranged below the support 40. The pressing unit 51 is provided witha pressing mandrel 53 having a central bore 54 into which a pressingpunch 55 is inserted. The pressing mandrel 53 is seated, for example, ina ball guide 56 in a low-friction manner, with the ball guide 56 beingreceived in a base body 57. The pressing mandrel 53 is provided with anelastic ring 58 on the side of the adjustment device, which ring pushesthe ball cage in its relaxed state back into the working position sothat during the pressing process only rolling friction and no slidingfriction occurs.

A pressing bell 60 is disposed between base body 57 and injection valve20, the bell being connected with the base body 57, for example, via twoguide pins 61, with the guide pins 61 being seated so as to be axiallydisplaceable within the base body 57. For example, four spring-biasedpins 62 project from the end face of the base body 57 on the injectionvalve side which act on the pressing bell 60 and press the b ell to theinjection valve 20 from the bottom by means of the spring force so thatthe axial clamping play of the injection valve 20 in the centering slide44 is eliminated.

The base body 57 is screwed to a yoke 63 which carries two guide bars 65to the feeding unit 52. The two guide bars 65 are each supported in twoguide sleeves 66 which are attached to the frame 11. Furthermore, anadvance unit 67 is also guided by the guide bars 65; in the presentembodiment, the advance unit is a ball screw drive. The advance unit 67is provided with two further sleeves 69 which are connected to a housing68, which sleeves implement the guidance of the advance unit 67 on theguide bars 66. The housing 68 comprises a thread nut 70 in which athreaded spindle 71 is guided. The threaded spindle 71 has a shaft, witha collar 73 being secured to it. The collar 73 is supported against anaxial/radial bearing 75 which rests on a support 76 which is fixed withrespect to the frame 11. On the threaded spindle 71 is seated a beltdisk 77 which is connected to a stepping motor which is not shown via atoothed belt 78.

On the drive side, a pot-shaped receiver 80 for a helical spring 81 isseated on the yoke 63. The yoke 63 has an opening 64 which is disposedcoaxially with respect to the pressing mandrel 53, with a sleeve 83having a force sensor 82 positioned in the opening. The sleeve 83comprises an overload protection. In the drive-side bottom, thepot-shaped receiver 80 is provided with a leadthrough 85 through whichextends a cylinder-shaped attachment 86 of the housing 68 and to whichend face a thrust plate 87 is secured on which a helical spring 81 isseated.

The adjustment path of the pressing mandrel 53 is generated by theadvance unit 67, during which process the generated pressing force istransmitted via the helical spring 81 and the force sensor 82 to thepressing mandrel 53. The force sensor 82 serves to recognize theapproach point of the pressing punch 55 on the apertured body 28 of theinjection valve 20. Furthermore, the force sensor 82 serves to monitorthe force values during the setting process.

The described apparatus works as follows:

An injection valve 20 is placed into the receiver 45 of the clampingdevice 40 and is clamped by means of the centering slide 44. Followingthe actuation of the centering slide 44, the adjustment unit 50 isguided to the nozzle-side end of the injection valve 20. This is done byactuating the stepping motor which is not shown, which causes theadvance unit 67 to feed the pressing unit 51, while beingforce-monitored by the force sensor 82, until the pressing punch 55rests against the apertured body 28 of the injection valve 20. Thissimultaneously presses the injection valve 20 against the centeringslide 44 of the clamping device 40 via the leading, spring-biasedpressing bell 60. In this manner it is ensured that the injection valve20 orients itself according to the infeed plane surface and is held bythe centering slide 44 without axial play.

The feeding cylinder 18 now feeds the measuring device 30 until the stop35 is seated on the injection valve 20 and the measuring gage 34 restson the valve closing body 25. Simultaneously with the feeding of themeasuring device 30, the magnetic circuit of the injection valve 20 iscontacted. After registering the lower position of the valve closingbody 25, the measuring gage 34 is lifted off the valve closing body 25and the magnetic circuit of the injection valve 20 is activated. Thisactuates the valve needle 24 and the valve closing body 25 is lifted offthe valve seat body 27. In this position of the valve closing body 25the measuring gage 34 is again placed on the valve closing body 25 andthe path sensing element 32 is set to zero. By removing the voltage forthe magnetic circuit, the valve closing body 25 falls back into theinitial position. In this manner the actual lift of the valve needle 24is determined.

Then the stepping motor which is not shown actuates the advance unit 67during which process the advance motion is picked up by the helicalspring 81 which acts as an energy store. On the basis of the springcharacteristic of the helical spring 81, the force stored in the helicalspring 81 due to the feeding motion of the advance unit 67 istransmitted via the force sensor 82 to the pressing mandrel 53 and thepressing punch 55 to the apertured body 28, with the apertured bodybeing plastically deformed due to the acting force of, for example, 1600to 1700 Newton at maximum. In this process the pressure spring 81 actsas transmission and allows a fast startup and feeding speed of thefeeding unit 52.

FIGS. 4a and 4b show a process sequence schedule for determining thefeeding path of the pressing punch 55 which is to be executed by theadjustment device 50 for the setting of the valve lift of the injectionvalve 20. By way of the preset actual lift of the valve needle 24 andthe desired set lift, the feeding path is detected as desireddifference. At the outset of the pressing process, a starting stepnumber for the stepping motor is determined according to step 100 bymeans of the desired difference as feed for the pressing punch 55. Thenthe determined step number is fed in step 101 and the feeding path thusobtained is read in according to step 102. The subsequent step 103 thenexamines whether the target value of the feeding path has been reached.If the target value has not been reached, a new step number isdetermined according to step 104 and the feeding path realized with thisstep number is measured again. Steps 101 to 104 are repeated until thetarget value according to step 103 is reached. Thus steps 101 to 104represent a learning phase.

Once the target value is reached, the pressing punch 55 is pulled back(step 105). During this process the apertured body 28 is relieved, whichcauses the apertured body 28 to spring back because of the portion ofthe elastic deformation. In this position the lift of the valve needle24 is measured again according to step 106 and according to step 107 itis examined whether the lift is within a preset tolerance. If the liftis within the preset tolerance, the pressing process is stopped (step108). If the lift is not within the preset tolerance, a computer unitwhich is not shown determines a characteristic according to step 109 byway of the values realized with the first feeding process. Thecharacteristic is not linear and has a different course for eachinjection valve, with the course being a function of several factors,for example, of the initial lift, the inclined position of the aperturedbody 28, of differences in material and geometry of the apertured body28 as well as of the spring-back path and the elasticity which may varydue to the welding of the apertured body 28. By way of thecharacteristic determined in step 109, the step number for a secondfeeding process necessary to accomplish the desired valve lift isdetermined in step 110 and the desired feeding path is calculated as asecond target value in step 111. Subsequently, the stepping motor is fedwith the step number determined from the characteristic (step 112) andthe feeding path is measured again (step 113). Step 114 examines whetherthe measured feeding path has reached the new target value of thedesired feeding path. If the condition according to step 114 is not met,a correction step number is calculated according to step 115 and steps112, 113, 114 and 115 are repeated until the condition according to step114 is met.

In step 116 the pressing punch 55 is again pulled back and thus theapertured body 28 is relieved. In the relieved state, the valve needlelift is again determined by the measuring device 30 (step 117). It isexamined according to step 118 if the valve needle lift is within thetolerance range. If the tolerance range is reached, the pressing processis stopped (step 119).

If the determined valve needle lift is not within the tolerance, it isexamined in step 120 whether the valve needle lift is still too large.If the condition according to step 120 is not met, the valve liftalready falls short of the desired valve lift and the injection valve isrejected according to step 121. If, however, the lift is still toolarge, the number of feeding processes is polled in step 122. If, forexample, feeding took place three times already, the injection valve isrejected as well according to step 121. If less than three feedingprocesses have been executed, the program returns to step 110 and a stepnumber and a further target value for a feeding path of a third feedingprocess are again determined from the characteristic. Steps 111 to 122repeat themselves accordingly.

The method is not limited to setting the valve lift of injection valves.It can be applied to all lift settings in which at least one liftlimitation is set by way of deformation.

We claim:
 1. An apparatus for adjusting a valve lift, particularly avalve needle lift of an injection valve of an internal combustionengine, by means of which a valve seat, which is preset in a housing ofthe valve, is axially displaceable in the housing by means of plasticdeformation, characterized in that an adjustment device (50) is providedwhich generates a feeding motion for a pressing tool (53, 55) in thedirection of the plastic deformation and that a measuring device (30) isarranged which determines the valve lift which is changeable by way ofthe plastic deformation of the valve seat and compares the valve liftwith a preset desired value, and that the adjustment device (50) can becontrolled by way of the desired value/actual value comparison.
 2. Anapparatus according to claim 1, characterized in that a spring element(81) is arranged between adjustment device and pressing tool (53, 55)which spring element transforms the feeding motion into a force for thepressing tool (53, 55) by utilizing an elastic form change.
 3. Anapparatus according to claim 2, characterized in that the spring element(81) is a pressure spring.
 4. An apparatus according to claim 1,characterized in that a force sensor (82) is arranged between adjustmentdevice (50) and pressing tool (53, 55) by means of which force sensorthe stop of the pressing tool (53, 55) at the valve seat can bedetermined by means of a reliable, set initial force.
 5. An apparatusaccording to claim 1, characterized in that the adjustment device (50)comprises a pressing unit (51) and a feeding unit (52), that thepressing unit (51) is provided with a low-friction guide (56) for thepressing tool (53, 55), and that the feeding unit (52) is embodied as aball screw drive (67) which generates the feeding motion.
 6. Anapparatus according to claim 5, characterized in that the ball screwdrive (52) is guided by a guide (65, 66) which is held on a base body(11) and that the ball screw drive (52) can be driven by a steppingmotor.
 7. An apparatus according to claim 1, characterized in that aclamping device (40) is provided which clamps the valve (20) by means ofa centering slide (44).
 8. An apparatus according to claim 7,characterized in that the valve (20) can be clamped by the centeringslide 44 while having an axial play and that the adjustment device (50)is provided with a work receiving attachment (60) acting on the valve(20), which attachment overcomes the axial play caused by the centeringslide (44) by means of a clamping force which axially acts on the valve(20).
 9. An apparatus according to claim 8, characterized in that thework receiving attachment (60) is seated on the adjustment device (50)so as to be spring-biased such that the spring force generates the axialclamping force.
 10. A method for setting a valve lift, particularly avalve needle lift of an injection valve, wherein by means of a pressingtool a preset valve seat is axially adjusted by plastic deformation,characterized in that the pressing tool is fed by way of a first feedingprocess and that, based on the values realized during the first feedingprocess, a characteristic is formed from which a further feed for atleast one further feeding process is determined.
 11. A method accordingto claim 10, characterized in that the characteristic is determined fromat least two successive feeds and from the feeding path realized therebyduring the first feeding process.
 12. A method according to claim 10,characterized in that the further feed is determined from thecharacteristic and the momentary valve lift.
 13. A method according toclaim 12, characterized in that the momentary valve lift is determinedin the relieved state of the valve seat.
 14. A method according to claim10, characterized in that a step number of a stepping motor is used asfeed.
 15. A method according to claim 10, characterized in that, afterthe first feeding process, the deformation of the valve seat is stoppedif the valve lift has already been reached by means of this feedingprocess.